A muscle that has a pattern of fascicles running along the long axis of the muscle has which of the following fascicle arrangements?
a. circular
b. pennate
c. parallel
d. rectus
The Correct Answer and Explanation is :
The correct answer is c. parallel.
Explanation:
A muscle with fascicles running along the long axis of the muscle exhibits a parallel fascicle arrangement. In this arrangement, the fascicles (bundles of muscle fibers) are oriented in a straight line, running parallel to the muscle’s long axis. This allows for maximum shortening of the muscle, which is useful for muscles involved in movements that require a large range of motion.
The parallel arrangement of fascicles can be found in muscles like the sartorius and the rectus abdominis, both of which are involved in relatively simple, linear movements. In these muscles, the fascicles run in the same direction as the muscle itself, which means that when the muscle contracts, it can pull along the full length of the muscle, allowing for greater movement flexibility.
The other fascicle arrangements are:
- a. Circular: In this arrangement, the fascicles are arranged in concentric circles. Muscles with this arrangement, such as the orbicularis oris (around the mouth), function to close or constrict an opening. The contraction of circular muscles tightens the circle, closing the opening they surround.
- b. Pennate: In a pennate arrangement, the fascicles are short and attach at an angle to a central tendon, resembling the structure of a feather. There are three types of pennate muscles: unipennate, bipennate, and multipennate. This arrangement allows for more muscle fibers in a given area, providing greater force production but sacrificing some range of motion. Examples include the rectus femoris and deltoid muscles.
- d. Rectus: This term refers to a type of parallel arrangement of muscle fibers where the muscle fibers run straight. It is often used in the naming of muscles like the rectus abdominis. It is essentially a synonym for parallel arrangement but emphasizes the straightness of the fibers.
Image Description:
I will generate an image to illustrate the parallel fascicle arrangement.
Here is the illustration of a muscle with a parallel fascicle arrangement, showing the long muscle fibers running along the axis of the muscle. This visual should help you better understand the arrangement of the muscle fibers.